This invention relates to a device for the sampling of body fluids, such as blood, urine, or tissue fluid, comprising a sampling unit connected to a hollow needle, and a storage system with several separate sample containers placed on a movable carrier, which are sealed so as to be gas-tight by means of puncturable membranes, and which are intended to receive collected fractions of the body fluid at given intervals, a device connected to a control unit being provided, which will permit the hollow needle to be positioned over each sample container in turn and to be inserted into the sample container through the membrane.
In medical applications it is often necessary to sample biological fluids, such as human or animal blood, urine, or tissue fluid, either continuously or intermittently. It would be desirable if such fluids could be collected 24 hours a day, i.e. during both day-time and night-time, without disturbing the patient's sleep, in order to obtain unbiased test results.
For such applications a new method is specified in WO 89/00397. Via a roller pump a few microliters of blood or tissue fluid (the latter being obtained by delivering a perfusion fluid into the tissue) are collected in capillary tubes, and a system of valves is used to establish a correspondence between the fluid samples and their withdrawal times.
This system requires a complex mechanism of valves, which will increase teh weight of the apparatus amongst others. In the individual sections of the capillary system the blood column may come to a halt, which might lead to the formation of clots in the system.
A device of the afore-mentioned type is presented in EP-A 0 223 758, for example. The apparatus for the handling of small fluid samples described there includes a rotatable fixture carrying a number of sample containers receiving the fluid samples by means of a hollow needle. The hollow needle is connected by a tube to a sampling unit, or rather, sampling needle (not discussed in detail) used for drawing the sample. The relative movement between hollow needle and sample container is provided by a special device permitting the needle to be properly inserted into the sample containers. For better protection of the needle its fitting is provided with a pressure sensor stopping any further movement of the needle if the axial forces exceed a given limit. If membrane-sealed sample containers are used, attention should be paid to the change in interior pressure during sample manipulation. The solution to this problem offered in EP-A 0 223 758, i.e., a needle with two bores, one of which provides the necessary pressure relief, is characterized by the disadvantage that sample components also may be released through this opening. This may lead to contamination of equipment of staff.
It is an object of the invention to develop a compact device on the basis of the afore-mentioned design, which may be attached to the patient even for prolonged periods of time, and will permit fluid samples, such as blood, urine, or tissue fluid, to be gathered safely and stored until further processing, regardless of the physical location of the device.